Exemplary embodiments of the present invention relate to a method for fabricating a semiconductor device, and more particularly, to a plasma doping method and a method for fabricating a semiconductor device using the same.
When a specific region is doped during a fabrication process of a semiconductor device, an ion beam implantation method is usually used. The ion beam implantation method is also referred to as a “beam line implantation method.”
As semiconductor devices become highly integrated, complicated three-dimensional (3D) structures are being developed, but however, doping of 3D structures through the ion beam implantation method is reaching its limits.
Such a concern in doping of 3D structures is described in detail below in reference to FIG. 1. To briefly explain the background, when a particular region of a conductive structure is to be selectively doped through the ion beam implantation method, the doping is performed at a predetermined angle. This is called “tilt ion implantation.”
More specifically, FIG. 1 illustrates a tilt ion implantation doping method for a semiconductor device.
Referring to FIG. 1, a substrate 11 including a plurality of conductive structures 12 is formed. The plurality of conductive structures 12 are formed over the substrate 11 with a predetermined space between them.
To dope a specific region of a conductive structure 12, the doping is performed through a tilt ion implantation method (see reference numeral ‘13’) because the gap between the conductive structures 12 is narrow and the conductive structures 12 are formed to have a predetermined height.
The tilt ion implantation 13 is performed at a certain tilt angle. However, a concern may arise in that a target region is not doped due to a shadow cast by, for example, the area 13A of a neighboring conductive structure 12 during the tilt ion implantation 13.
Also, although the tilt ion implantation 13 is performed, it is difficult to dope a doping target region with a desired level of doping concentration and a desired doping depth because the conductive structures 12 may be relatively tall and the gap between the conductive structures 12 may be relatively narrow.
Another way for doping a specific region of a 3D conductive structure is a method using a doped material such as doped polysilicon. When a doped material is used, a target region is doped by thermally diffusing the dopant of the doped material through an annealing process.
However, when a region is doped through thermal diffusion, it is difficult to control the doping depth and the doping dose. Further, when the doped material is removed for a subsequent process, a dopant loss occurs. Still further, it is hard to remove the doped material. Moreover, since the thermal diffusion method does not adequately control the doping depth when a shallow doping depth is required, floating body effect may occur.